The Dancing With The Stars contestant, who is renown for her supreme figure, admits that she has a great fear about stripping down.
'I have some serious issues here,' she told Allure. 'But I want to get over that.'
'Two years ago, a wave hit me in the ocean, and when I came out of the water, half of my special area was exposed,' she told the magazine. 'The paparazzi took pictures. It was mortifying. I thought I was going to die.'
Meanwhile, Smash star Messing doesn't have a problem getting naked and quite happily shed any inhibitions for the stunning shoot.
The 43-year-old actress, who has an eight-year-old son Roman with her estranged husband Daniel Zelman, says her relationship with her body has changed over the years.
'Once you have a child, once you pass 40, you have a different relationship with your body,' she said. 'I love my body in a way I never have before.'
The 38-year-old German supermodel, who has four children, put her lean figure on show while using only her arms to preserve her modesty.
Cover girl: Heidi Klum is on the new issue of Allure
She told Allure: 'I'm proud to be able to say, in this day and age, I haven't done anything. Everyone has a view of what's not pretty and [plastic surgery] just doesn't look pretty to me. Especially when I see it on really young girls.
'I don’t want to name names, but it’s like, wow, I remember you five years ago, looking to me so beautiful, and now it’s like … who is this person? And I know girls half my age who do it. What are they gonna do at 40 or 50, when the s*** really hits the fan?”
Heidi also opened up about her split from singer Seal, describing the end of her marriage as a 'curveball.
The pair split in January after seven years of marriage and Heidi is still figuring out how to adjust to the changes in her life.
She told the magazine: 'Sometimes life throws you a curveball, and then you just figure it out and deal with it, but my dream always was that – to have the perfect family and have lots of children and a beautiful garden and trampolines and swings and things.
'I had dreams of how I wanted things to be and planned for things and, as we all know today, they don't always turn out as you dreamt them in your head.'
Heidi - who raises children Leni, seven, Henry, six, Johan, five, and two-year-old Lou with Seal - added she doesn't feel any resent about the split, which her former husband has said was caused by them growing apart.
She added: 'I don’t resent anything that ever happened. Things just turn out the way they turn out.'
The May issue of Allure is on stands in the US on April 24.